Manufacturing Method for Alloy Material, Alloy Material, Electrochemical Element, Electrochemical Module, Electrochemical Device, Energy System and Solid Oxide Fuel Cell

ABSTRACT

Provided is an alloy material including a metal oxide thin layer that can be formed using a simple method at low cost and can further suppress volatilization of Cr, which causes deterioration of a fuel cell, compared with a case where conventional expensive materials are used. Disclosed is a manufacturing method for an alloy material including a coating treatment step for coating a substrate made of a Fe—Cr based alloy with Co, and an oxidation treatment step for performing oxidation treatment on the substrate in a moisture-containing atmosphere after the coating treatment step.

TECHNICAL FIELD

The present invention relates to an alloy material to be used in anelectrochemical device, a solid oxide fuel cell, and the like, and amanufacturing method for the alloy material.

BACKGROUND ART

A material obtained by forming a steam oxidation suppressing layerincluding a MnCr oxide layer and a composite oxide layer that containsMn and Co, and the like on the surface of a Cr alloy material throughapplication of slurry and oxidation treatment has been used as aconventional heat-resistant alloy material for a solid oxide fuel cell(Patent Document 1).

PRIOR ART DOCUMENTS Patent Document

Patent Document 1: JP 2010-250965A

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention

With the method for applying a complex composite oxide layer on/over analloy material as disclosed in Patent Document 1, the manufacturing costof the alloy material is high. In addition, there is room forimprovement in suppression of volatilization of Cr.

The present invention was achieved in light of the foregoing problems,and an object of the present invention is to provide an alloy materialincluding a metal oxide thin layer that can be formed using a simplemethod at low cost and can further suppress volatilization of Cr, whichcauses deterioration of a fuel cell, compared with a case whereconventional expensive materials are used.

Means for Solving Problem

A characteristic configuration of a manufacturing method for an alloymaterial for achieving the object includes a coating treatment step forcoating a substrate made of a Fe—Cr based alloy with Co, and anoxidation treatment step for performing oxidation treatment on thesubstrate in a moisture-containing atmosphere after the coatingtreatment step.

The above-mentioned characteristic configuration makes it possible tomanufacture an alloy material having high thermal resistance at lowcost. In addition, an effect of suppressing volatilization of Cr can beimproved compared with conventional cases.

In another characteristic configuration of the manufacturing method foran alloy material according to the present invention, coating with Co isperformed through plating treatment in the coating treatment step.

The above-mentioned characteristic configuration makes it possible tomanufacture an alloy material at lower cost.

It is preferable to perform the oxidation treatment step in anatmosphere having a dew point of 25° C. or higher because an alloymaterial that exhibits a large effect of suppressing volatilization ofCr can be manufactured. It is more preferable to perform the oxidationtreatment step in an atmosphere having a dew point of 30° C. or higher,and it is even more preferable to perform the oxidation treatment stepin an atmosphere having a dew point of 35° C. or higher. The reason forthis is that manufacturing an alloy material that exhibits a largereffect of suppressing volatilization of Cr is facilitated.

A characteristic configuration of an alloy material for achieving theobject includes a substrate made of a Fe—Cr based alloy, and a thinlayer formed on/over the substrate, wherein the thin layer contains Co,and a Co-containing region is formed in the vicinity of a surface insidethe substrate.

With the above-mentioned characteristic configuration, the thin layercontains Co, and the Co-containing region is formed in the vicinity ofthe surface inside the substrate. An alloy material having such aconfiguration exhibits an improved effect of suppressing volatilizationof Cr and is favorably used in an electrochemical element, anelectrochemical device, a solid oxide fuel cell, or the like.

A characteristic configuration of an alloy material for achieving theobject includes a substrate made of a Fe—Cr based alloy, and a thinlayer formed on/over the substrate, wherein the thin layer includes afirst layer and a second layer,

the first layer is formed on/over the substrate and is made of a metaloxide that contains Cr, and

the second layer is formed on/over the first layer as a metal oxide thinlayer containing Co.

With the above-mentioned characteristic configuration, the alloymaterial provided with the thin layer that includes the first layercontaining Cr and the second layer containing Co is formed. An alloymaterial having such a configuration exhibits an improved effect ofsuppressing volatilization of Cr and is favorably used in anelectrochemical element, an electrochemical device, a solid oxide fuelcell, or the like.

A characteristic configuration of an alloy material for achieving theobject includes a substrate made of a Fe—Cr based alloy, and a thinlayer formed on/over the substrate, wherein the thin layer includes afirst layer and a second layer,

the first layer is formed on/over the substrate and is made of a metaloxide containing Cr,

the second layer is formed on/over the first layer and is made of ametal oxide containing Co, and

a Co-containing region is formed in the vicinity of a surface inside thesubstrate.

With the above-mentioned characteristic configuration, the thin layerincludes the first layer containing Cr and the second layer containingCo, and the Co-containing region is formed in the vicinity of thesurface inside the substrate. An alloy material having such aconfiguration exhibits an improved effect of suppressing volatilizationof Cr and is favorably used in an electrochemical element, anelectrochemical device, a solid oxide fuel cell, or the like.

It is more preferable that the second layer contains Mn because an alloymaterial that exhibits an improved effect of suppressing volatilizationof Cr is formed.

It is more preferable that the Fe—Cr based alloy of the substratecontains Mn in an amount of 0.05 mass % or more because an alloymaterial including a thin layer that exhibits an improved effect ofsuppressing volatilization of Cr is easily obtained. It is even morepreferable that the content of Mn is 0.1 mass % or more because an alloymaterial including a thin layer that exhibits an improved effect ofsuppressing volatilization of Cr is more easily obtained.

In another characteristic configuration of the alloy material accordingto the present invention, the Fe—Cr based alloy of the substrate is anyone of a Fe—Cr based alloy that contains Ti in an amount of 0.15 mass %or more and 1.0 mass % or less, a Fe—Cr based alloy that contains Zr inan amount of 0.15 mass % or more and 1.0 mass % or less, and a Fe—Crbased alloy that contains Ti and Zr, the total content of Ti and Zrbeing 0.15 mass % or more and 1.0 mass % or less.

Ti and Zr are likely to form stable carbides through reaction withcarbon in a steel material. With the above-mentioned characteristicconfiguration, a metal support is made of any one of a Fe—Cr based alloythat contains Ti in an amount of 0.15 mass % or more and 1.0 mass % orless, a Fe—Cr based alloy that contains Zr in an amount of 0.15 mass %or more and 1.0 mass % or less, and a Fe—Cr based alloy that contains Tiand Zr, the total content of Ti and Zr being 0.15 mass % or more and 1.0mass % or less, and the effect of improving oxidation resistance andhigh-temperature strength of the Fe—Cr based alloy is thus obtained,thus making it possible to suppress volatilization of Cr from the metalsupport even during long periods of use at high temperatures, and makingit possible to realize an electrochemical element that has excellentdurability.

It should be noted that the content of Ti is preferably 0.20 mass % ormore, and more preferably 0.25 mass % or more. The reason for this isthat the effect of improving oxidation resistance and high-temperaturestrength of the Fe—Cr based alloy due to the addition of Ti or Zr can bemade greater. Moreover, the content of Ti is preferably 0.90 mass % orless, and more preferably 0.80 mass % or less. The reason for this isthat an increase in the cost of the Fe—Cr based alloy due to theaddition of Ti or Zr can be suppressed.

It should be noted that the content of Zr is preferably 0.20 mass % ormore, and more preferably 0.25 mass % or more. The reason for this isthat the effect of improving oxidation resistance and high-temperaturestrength of the Fe—Cr based alloy due to the addition of Ti or Zr can bemade greater. Moreover, the content of Zr is preferably 0.90 mass % orless, and more preferably 0.80 mass % or less. The reason for this isthat an increase in the cost of the Fe—Cr based alloy due to theaddition of Ti or Zr can be suppressed.

It should be noted that the total content of Ti and Zr is preferably0.20 mass % or more, and more preferably 0.25 mass % or more. The reasonfor this is that the effect of improving oxidation resistance andhigh-temperature strength of the Fe—Cr based alloy due to the additionof Ti or Zr can be made greater. Moreover, the total content of Ti andZr is preferably 0.90 mass % or less, and more preferably 0.80 mass % orless. The reason for this is that an increase in the cost of the Fe—Crbased alloy due to the addition of Ti or Zr can be suppressed.

In another characteristic configuration of the alloy material accordingto the present invention, the Fe—Cr based alloy of the substratecontains Cu in an amount of 0.10 mass % or more and 1.0 mass % or less.

Cu has an effect of reducing contact resistance (electric resistance).With the above-mentioned characteristic configuration, the metal supportcontains Cu in an amount of 0.10 mass % or more and 1.0 mass % or less,thus making it possible to suppress the electric resistance value of theelectrochemical element to a low level, and making it possible torealize a high-performance electrochemical element.

It should be noted that the content of Cu is preferably 0.20 mass % ormore, and more preferably 0.30 mass % or more. The reason for this isthat the effect of reducing contact resistance due to the addition of Cuto the Fe—Cr based alloy can be made greater. Moreover, the content ofCu is preferably 0.90 mass % or less, and more preferably 0.70 mass % orless. The reason for this is that an increase in cost due to theaddition of Cu to the Fe—Cr based alloy can be suppressed.

In another characteristic configuration of the alloy material accordingto the present invention, the Fe—Cr based alloy of the substratecontains Cr in an amount of 18 mass % or more and 25 mass % or less.

The above-mentioned characteristic configuration makes it possible tobring the thermal expansion coefficient of the Fe—Cr based alloy closeto the thermal expansion coefficients of a zirconia-based material and aceria-based material contained in the materials for forming an electrodelayer and an electrolyte layer of a SOFC, for example, thus making itpossible to suppress breakage and separation of the electrode layer andthe electrolyte layer even in a case where the electrochemical elementis used at high temperatures or a heat cycle is performed, and making itpossible to realize a highly reliable electrochemical element.

It should be noted that the content of Cr is more preferably 20 mass %or more. The reason for this is that the thermal expansion coefficientof the Fe—Cr based alloy can be brought closer to the thermal expansioncoefficients of the zirconia-based material and the ceria-basedmaterial. Moreover, the upper limit of the content of Cr is morepreferably 23 mass % or less. The reason for this is that an increase inthe cost of the Fe—Cr based alloy can be suppressed.

An electrochemical element in which at least an electrode layer, anelectrolyte layer, and a counter electrode layer are provided on/overthe above-described alloy material has high performance because thevolatilization of Cr from the alloy material is suppressed and the alloymaterial functions as a metal support of the electrochemical element.

In a characteristic configuration of an electrochemical module accordingto the present invention, a plurality of the above-describedelectrochemical elements are arranged in an assembled state.

With the above-mentioned characteristic configuration, the plurality ofthe above-described electrochemical elements are arranged in anassembled state, thus making it possible to obtain an electrochemicalmodule that is compact, has high performance, and has excellent strengthand reliability, while also suppressing material cost and processingcost.

A characteristic configuration of an electrochemical device according tothe present invention includes at least the above-describedelectrochemical module and a reformer, and includes a fuel supply unitwhich supplies fuel gas containing a reducible component to theelectrochemical module.

The above-mentioned characteristic configuration includes theelectrochemical module and the reformer, and includes the fuel supplyunit which supplies the fuel gas containing a reducible component to theelectrochemical module, thus making it possible to realize anelectrochemical device that uses an existing raw fuel supplyinfrastructure such as city gas and includes the electrochemical modulethat has excellent durability, reliability, and performance. Also, it iseasier to construct a system that recycles unused fuel gas dischargedfrom the electrochemical module, thus making it possible to realize ahighly efficient electrochemical device.

A characteristic configuration of an electrochemical device according tothe present invention includes at least the above-describedelectrochemical module and an inverter that extracts electrical powerfrom the electrochemical module.

The above-mentioned characteristic configuration is preferable becauseit makes it possible to boost, using an inverter, electrical outputobtained from the electrochemical module that has excellent durability,reliability, and performance, or to convert a direct current into analternating current, and thus makes it easy to use the electrical outputobtained from the electrochemical module.

It is preferable that the electrochemical device includes a separatorand the above-described alloy material is used for the separator becausevolatilization of Cr from the separator is suppressed. It should benoted that the separator separates a fuel gas passage and an air passagethat supply fuel gas and air to the plurality of electrochemicalelements arranged in an assembled manner.

It is preferable that the electrochemical device includes a manifold andthe above-described alloy material is used for the manifold becausevolatilization of Cr from the manifold is suppressed. It should be notedthat the manifold supplies fuel gas or air to the plurality ofelectrochemical elements arranged in an assembled manner.

It is preferable that the electrochemical device includesinterconnectors and the above-described alloy material is used for theinterconnectors because volatilization of Cr from the interconnectors issuppressed. It should be noted that the interconnectors join theplurality of electrochemical elements to each other.

It is preferable that the electrochemical device includes a currentcollector and the above-described alloy material is used for the currentcollector because volatilization of Cr from the current collector issuppressed. It should be noted that the current collector has electronconductivity and is to be connected to the electrode layer of theelectrochemical element.

A characteristic configuration of an energy system according to thepresent invention includes the above-described electrochemical device,and a waste heat management unit that reuses heat discharged from theelectrochemical device.

The above-mentioned characteristic configuration includes theelectrochemical device and the waste heat management unit that reusesheat discharged from the electrochemical device, thus making it possibleto realize an energy system that has excellent durability, reliability,and performance as well as excellent energy efficiency. It should benoted that it is also possible to realize a hybrid system that hasexcellent energy efficiency by combination with a power generationsystem that generates power with use of combustion heat from unused fuelgas discharged from the electrochemical device.

A characteristic configuration of a solid oxide fuel cell according tothe present invention includes the above-described electrochemicalelement, wherein a power generation reaction is caused in theelectrochemical element.

The above-mentioned characteristic configuration makes it possible tosuppress deterioration of the electrochemical element and maintain theperformance of the fuel cell for a long period of time. It should benoted that a solid oxide fuel cell that can be operated in a temperaturerange of 650° C. or higher during the rated operation is more preferablebecause a fuel cell system that uses hydrocarbon-based raw fuel such ascity gas can be constructed such that waste heat discharged from a fuelcell can be used in place of heat required to convert raw fuel tohydrogen, and the power generation efficiency of the fuel cell systemcan thus be improved. A solid oxide fuel cell that is operated in atemperature range of 900° C. or lower during the rated operation is morepreferable because the effect of suppressing volatilization of Cr can bemaintained at a high level, and thus the long-term durability isexcellent. A solid oxide fuel cell that is operated in a temperaturerange of 850° C. or lower during the rated operation is even morepreferable because the effect of suppressing volatilization of Cr can befurther improved, and thus the long-term durability is excellent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing a configuration of anelectrochemical element.

FIG. 2 is a schematic diagram showing configurations of electrochemicalelements and an electrochemical module.

FIG. 3 is a schematic diagram showing configurations of anelectrochemical device and an energy system.

FIG. 4 is a schematic diagram showing a configuration of anelectrochemical module.

FIG. 5 shows the results of an element distribution measurement of aproduced sample (working example).

FIG. 6 shows the results of an element distribution measurement of aproduced sample (comparative example).

BEST MODES FOR CARRYING OUT THE INVENTION First Embodiment

Hereinafter, a manufacturing method for an alloy material according tothis embodiment and an alloy material will be described. The alloymaterial is manufactured by coating a substrate with Co and performingoxidation treatment in an atmosphere to which water vapor has beenadded. In the thus-manufactured alloy material, volatilization of Cr issuppressed, and the alloy material is favorably used in anelectrochemical element, an electrochemical device, a solid oxide fuelcell, and the like. For example, the alloy material is used for a metalsubstrate 1 (metal support) of an electrochemical element E shown inFIG. 1. For example, the alloy material is used for a U-shaped component7 (separator) or a current collector 26 of an electrochemical module Mshown in FIG. 2. For example, the alloy material is used for a gasmanifold 17 (manifold) of an electrochemical device Y shown in FIG. 3.

It should be noted that the alloy material may be constituted by asubstrate and a thin layer (metal oxide thin layer 1 b (diffusionsuppressing layer)) formed by directly coating the surface of thesubstrate with Co and then performing oxidation treatment.Alternatively, the alloy material may be constituted by a substrate, aninterposing layer between the substrate and a thin layer, and the thinlayer formed by coating the interposing layer with Co and thenperforming oxidation treatment.

Substrate

A Fe—Cr based alloy is used as the substrate of the alloy material. Itis preferable that the Fe—Cr based alloy of the substrate contains Mn inan amount of 0.05 mass % or more. It is more preferable that the Fe—Crbased alloy of the substrate is any one of a Fe—Cr based alloy thatcontains Ti in an amount of 0.15 mass % or more and 1.0 mass % or less,a Fe—Cr based alloy that contains Zr in an amount of 0.15 mass % or moreand 1.0 mass % or less, and a Fe—Cr based alloy that contains Ti and Zr,the total content of Ti and Zr being 0.15 mass % or more and 1.0 mass %or less. It is more preferable that the Fe—Cr based alloy of thesubstrate contains Cu in an amount of 0.10 mass % or more and 1.0 mass %or less. It is more preferable that the Fe—Cr based alloy of thesubstrate contains Cr in an amount of 18 mass % or more and 25 mass % orless.

Manufacturing Method for Alloy Material

Next, a manufacturing method for an alloy material according to thisembodiment will be described.

Coating Treatment Step

In a coating treatment step, the substrate made of a Fe—Cr alloy iscoated with Co. The substrate can be coated with Co through platingtreatment electrolytic plating or non-electrolytic plating), vapordeposition treatment, painting using paint containing Co, or the like.

It should be noted that, in the coating treatment step, the surface ofthe substrate may be directly coated with Co, or the interposing layerbetween the substrate and the thin layer may be coated with Co.

Oxidation Treatment Step

In an oxidation treatment step, the substrate is subjected to oxidationtreatment in a moisture-containing atmosphere. The dew point of theatmosphere is preferably 25° C. or higher, more preferably 30° C. orhigher, and even more preferably 35° C. or higher. The oxidationtreatment is preferably performed at a temperature of 600° C. or higher,and more preferably at a temperature of 700° C. or higher. The oxidationtreatment is preferably performed at a temperature of 1100° C. or lower,and more preferably at a temperature of 1050° C. or lower.

The alloy material can be manufactured as described above. It should benoted that, when the alloy material is used for the metal substrate 1,the separator, the manifold, the current collector, or the like of theelectrochemical element E, it is preferable to perform machineprocessing such as cutting, bending, or press shape forming on the alloymaterial before performing the coating treatment step and the oxidationtreatment step. It is also possible to perform machine processing suchas cutting or bending after performing the coating treatment step andthe oxidation treatment step.

Also, it is preferable to use the thus-obtained alloy material as themetal substrate 1 of the electrochemical element E because ahigh-performance electrochemical element E whose internal resistance issuppressed can be obtained.

WORKING EXAMPLES

Samples of the alloy material were produced using substrates having acomposition shown in Table 1 below. It should be noted that the unit forthe values in the composition shown in Table 1 is “mass %”. Thesubstrates were coated with Co through electrolytic plating. There werethree types of thicknesses of the Co coatings, namely 1 μm, 2 μm, and 3μm. Two conditions, namely an atmosphere having a dew point of 40° C.(working examples) and an atmosphere having a dew point of 20° C.(comparative examples), were used to perform the oxidation treatment. Inall the cases, the oxidation treatment was performed at temperatures850° C. (for 60 minutes) and 1000° C. (for 90 minutes), that is, as atwo-stage treatment.

TABLE 1 Si 0.094 Mn 0.17 Cu 0.43 Ni 0.18 Cr 20.82 Al 0.04 Mo 0.053 Nb0.008 Ti 0.325 Zr — La —

The amount of volatilized Cr was measured for each of the six types ofproduced samples. Metal plate samples with a width of 25 mm and a lengthof 250 to 300 mm were used and exposed to air at 0.5 L/minute (dewpoint: 20° C. or 40° C.) at a temperature of 850° C. for 100 hours.Then, the amount (integrated amount) of Cr volatilized during that timewas measured. Table 2 shows the measurement results. It should be notedthat the unit for the amounts of volatilized Cr shown in Table 2 is“μg/600 cm²”, and the values obtained through conversion into valuescorresponding to the amount of Cr volatilized from a metal surface areaof 600 cm² are shown.

TABLE 2 Coating thickness Amount of volatilized Cr Comp. Ex. 1 μm 310 μg(oxidation treatment was 2 μm 544 μg performed in atmosphere 3 μm 643 μghaving dew point of 20° C.) Work. Ex. 1 μm  12 μg (oxidation treatmentwas 2 μm smaller than or equal to performed in atmosphere detectionlimit having dew point of 40° C.) 3 μm smaller than or equal todetection limit

In the three types of samples of the comparative examples, a certainamount of Cr volatilized. In contrast, in the three types of samples ofthe working examples, the amount of volatilized Cr was very small. Inparticular, in the two types of samples having a coating thickness of 2μm or more, the amount of volatilized Cr was smaller than or equal tothe detection limit. It was found from these results that an alloymaterial in which the amount of volatilized Cr is very small can beobtained using the manufacturing method for an alloy material accordingto this embodiment.

In the produced samples of the working example and the comparativeexample, the element distributions (Cr, Fe, Mn, Co) in the vicinity ofthe surface were measured. The analyses were performed by exposing crosssections of the alloy materials and performing EPMA analysis thereon.FIGS. 5 and 6 show the results.

FIG. 5 shows the results from the working example (the oxidationtreatment was performed in the atmosphere having a dew point of 40° C.,and the coating thickness was 3 μm). The horizontal axis indicatespositions (unit: mm) in the direction orthogonal to the surface of thesubstrate. The rightward direction (positive direction) is a directiontoward the surface of the substrate, and the leftward direction(negative direction) is a direction toward the inside of the substrate.The vertical axis indicates the signal intensity of each element, whichis a relative value, and thus the distribution ratio between theelements is not reflected.

Focusing on the distribution of Fe, the signal intensity was highbetween position 0 to position 0.005, the signal intensity decreased inthe vicinity of a position between position 0.005 to position 0.006, andthe signal intensity was substantially zero from position 0.007 onward.Accordingly, it was estimated that the vicinity of a portion betweenposition 0 to position 0.006 corresponded to the substrate (alloy), anda portion on the right side (surface side) of position 0.006corresponded to the thin layer.

A large amount of Cr was distributed between position 0.006 to position0.009. Accordingly, it was estimated that Cr was distributed in a regionof the thin layer near the substrate. A large amount of Mn wasdistributed between position 0.009 to position 0.013. Accordingly, itwas estimated that a large amount of Mn was distributed in a region ofthe thin layer that was far from the substrate and in which a smallamount of Cr was distributed. A large amount of Co was distributedbetween position 0.003 and position 0.006, and between position 0.009and position 0.013. Accordingly, it was estimated that Co wasdistributed in two regions. One was a region inside the substrate thatwas located in the vicinity of the interface between the substrate andthe thin layer, that is, in the vicinity of the surface of thesubstrate. The other was a region of the thin layer that was far fromthe substrate and in which a small amount of Cr was distributed, thatis, the same region as in the case of Mn.

It was confirmed from the above-described results of the elementdistributions that the thin layer was formed in the vicinity of thesurface of the substrate in the alloy material according to thisembodiment. The thin layer was formed on/over the substrate (formedabove the substrate, formed to be in contact with the substrate, orformed near the substrate), and included a first layer and a secondlayer formed on/over the first layer (formed above the first layer,formed to be in contact with the first layer, or formed near the firstlayer). The first layer contained a large amount of Cr. The second layercontained a large amount of Co and a large amount of Mn. A region(Co-containing region) that contained Co was formed in the vicinity ofthe surface inside the substrate.

FIG. 6 shows the results from the comparative example (the oxidationtreatment was performed in the atmosphere having a dew point of 20° C.,and the coating thickness was 3 μm).

Focusing on the distribution of Fe, the signal intensity was highbetween position 0 to position 0.006, the signal intensity decreased inthe vicinity of a position between position 0.006 to position 0.008, andthe signal intensity was substantially zero from position 0.008 onward.Accordingly, it was estimated that the vicinity of a portion betweenposition 0 to position 0.008 corresponded to the substrate (alloy), anda portion on the right side (surface side) of position 0.008corresponded to the thin layer.

A large amount of Cr was distributed between position 0.007 to position0.012. Accordingly, it was estimated that Cr was widely distributed inthe thin layer region. A large amount of Mn was distributed betweenposition 0.010 to position 0.012. Accordingly, it was estimated that alarge amount of Mn was distributed in a region of the thin layer thatwas far from the substrate. Unlike the case of the working example shownin FIG. 5, the region in which Mn was distributed and the region inwhich Cr was distributed overlapped each other. A large amount of Co wasdistributed between position 0 and position 0.008. Unlike the case ofthe working example shown in FIG. 5, it was estimated that Co wasdistributed inside the substrate.

As shown in FIG. 6, Cr was distributed in the entire thin layer in thecomparative example. On the other hand, in the case of the workingexample shown in FIG. 5, a large amount of Mn and a large amount of Cowere distributed in the vicinity of the surface of the thin layer, but asmall amount of Cr was distributed therein. It is thought that such aconfiguration makes it possible to significantly reduce the amount ofvolatilized Cr.

Second Embodiment

Hereinafter, an electrochemical element E and a solid oxide fuel cell(SOFC) according to this embodiment will be described with reference toFIG. 1. The electrochemical element E is used as a constituent elementof a solid oxide fuel cell that receives a supply of air and fuel gascontaining hydrogen and generates power, for example. It should be notedthat when the positional relationship between layers and the like aredescribed in the description below, a counter electrode layer 6 side maybe referred to as “upper portion” or “upper side”, and an electrodelayer 2 side may be referred to as “lower portion” or “lower side”, withrespect to an electrolyte layer 4, for example. In addition, in a metalsubstrate 1, a surface on/over which the electrode layer 2 is formed maybe referred to as “front side”, and a surface on an opposite side may bereferred to as “back side”.

Electrochemical Element

As shown in FIG. 1, the electrochemical element E includes a metalsubstrate 1 (metal support), an electrode layer 2 formed on/over themetal substrate 1, an intermediate layer 3 formed on/over the electrodelayer 2, and an electrolyte layer 4 formed on/over the intermediatelayer 3. The electrochemical element E further includes a reactionpreventing layer 5 formed on/over the electrolyte layer 4, and a counterelectrode layer 6 formed on/over the reaction preventing layer 5.Specifically, the counter electrode layer 6 is formed above theelectrolyte layer 4, and the reaction preventing layer 5 is formedbetween the electrolyte layer 4 and the counter electrode layer 6. Theelectrode layer 2 is porous, and the electrolyte layer 4 is dense.

Metal Substrate

The metal substrate 1 plays a role as a support that supports theelectrode layer 2, the intermediate layer 3, the electrolyte layer 4,and the like and maintains the strength of the electrochemical elementE. In this embodiment, the above-described alloy material is used as themetal substrate 1. It should be noted that although a plate-shaped metalsubstrate 1 is used as the metal support in this embodiment, a metalsupport having another shape such as a box shape or cylindrical shapecan also be used.

It should be noted that the metal substrate 1 need only have a strengthsufficient for serving as the support for forming the electrochemicalelement, and can have a thickness of approximately 0.1 mm to 2 mm,preferably approximately 0.1 mm to 1 mm, and more preferablyapproximately 0.1 mm to 0.5 mm, for example.

The metal substrate 1 is provided with a plurality of through holes 1 athat penetrate the surface on the front side and the surface on the backside. It should be noted that the through holes 1 a can be provided inthe metal substrate 1 through mechanical, chemical, or optical piercingprocessing, for example. The through holes 1 a have a function oftransmitting gas from the surface on the back side of the metalsubstrate 1 to the surface on the front side thereof. Porous metal canalso be used to impart gas permeability to the metal substrate 1. Ametal sintered body, a metal foam, or the like can also be used as themetal substrate 1, for example.

When a ferrite-based stainless steel material is used as a material ofthe substrate of the metal substrate 1, its thermal expansioncoefficient is close to that of YSZ (yttria-stabilized zirconia), GDC(gadolinium-doped ceria; also called CGO), or the like, which is used asthe material for forming the electrode layer 2 and the electrolyte layer4. Accordingly, even if low and high temperature cycling is repeated,the electrochemical element E is not likely to be damaged. Therefore,this is preferable due to being able to realize an electrochemicalelement E that has excellent long-term durability.

Electrode Layer

As shown in FIG. 1, the electrode layer 2 can be provided as a thinlayer in a region that is larger than the region provided with thethrough holes 1 a, on/over the front surface of the metal substrate 1.When it is provided as a thin layer, the thickness can be set toapproximately 1 μm to 100 μm, and preferably 5 μm to 50 μm, for example.This thickness makes it possible to ensure sufficient electrodeperformance while also achieving cost reduction by reducing the usedamount of expensive electrode layer material. The region provided withthe through holes 1 a is entirely covered with the electrode layer 2.That is, the through holes 1 a are formed inside the region of the metalsubstrate 1 in which the electrode layer 2 is formed. In other words,all the through holes 1 a are provided facing the electrode layer 2.

A composite material such as NiO-GDC, Ni-GDC, NiO-YSZ, Ni-YSZ, CuO—CeO₂,or Cu—CeO₂ can be used as the material for forming the electrode layer2, for example. In these examples, GDC, YSZ, and CeO₂ can be called theaggregate of the composite material. It should be noted that it ispreferable to form the electrode layer 2 using low-temperature heating(not performing heating treatment in a high temperature range of higherthan 1100° C., but rather performing a wet process using heatingtreatment in a low temperature range, for example), a spray coatingtechnique (a technique such as a thermal spraying technique, an aerosoldeposition technique, an aerosol gas deposition technique, a powder jetdeposition technique, a particle jet deposition technique, or a coldspraying technique), a PVD technique (e.g., a sputtering technique or apulse laser deposition technique), a CVD technique, or the like. Due tothese processes that can be used in a low temperature range, a favorableelectrode layer 2 is obtained without using heating in a hightemperature range of higher than 1100° C., for example. Therefore, thisis preferable due to being able to prevent damage to the metal substrate1, suppress element interdiffusion between the metal substrate 1 and theelectrode layer 2, and realize an electrochemical element that hasexcellent durability. Furthermore, using low-temperature heating makesit possible to facilitate handling of raw materials and is thus morepreferable.

The inside and the surface of the electrode layer 2 are provided with aplurality of pores in order to impart gas permeability to the electrodelayer 2.

That is, the electrode layer 2 is formed as a porous layer. Theelectrode layer 2 is formed to have a denseness of 30% or more and lessthan 80%, for example. Regarding the size of the pores, a size suitablefor smooth progress of an electrochemical reaction can be selected asappropriate. It should be noted that the “denseness” is a ratio of thematerial of the layer to the space and can be represented by a formula“1—porosity”, and is equivalent to relative density.

Intermediate Layer

As shown in FIG. 1, the intermediate layer 3 can be formed as a thinlayer on/over the electrode layer 2 so as to cover the electrode layer2. When it is formed as a thin layer, the thickness can be set toapproximately 1 μm to 100 μm, preferably approximately 2 μm to 50 μm,and more preferably approximately 4 μm to 25 μm, for example. Thisthickness makes it possible to ensure sufficient performance while alsoachieving cost reduction by reducing the used amount of expensiveintermediate layer material. YSZ (yttria-stabilized zirconia), SSZ(scandium-stabilized zirconia), GDC (gadolinium-doped ceria), YDC(yttrium-doped ceria), SDC (samarium-doped ceria), or the like can beused as the material for forming the intermediate layer 3. Inparticular, ceria-based ceramics are favorably used.

It is preferable to form the intermediate layer 3 using low-temperatureheating (not performing heating treatment in a high temperature range ofhigher than 1100° C., but rather performing a wet process using heatingtreatment in a low temperature range, for example), a spray coatingtechnique (a technique such as a thermal spraying technique, an aerosoldeposition technique, an aerosol gas deposition technique, a powder jetdeposition technique, a particle jet deposition technique, or a coldspraying technique), a PVD technique (e.g., a sputtering technique or apulse laser deposition technique), a CVD technique, or the like. Due tothese film formation processes that can be used in a low temperaturerange, an intermediate layer 3 is obtained without using heating in ahigh temperature range of higher than 1100° C., for example. Therefore,it is possible to prevent damage to the metal substrate 1, suppresselement interdiffusion between the metal substrate 1 and the electrodelayer 2, and realize an electrochemical element E that has excellentdurability. Furthermore, using low-temperature heating makes it possibleto facilitate handling of raw materials and is thus more preferable.

It is preferable that the intermediate layer 3 has oxygen ion (oxideion) conductivity. It is more preferable that the intermediate layer 3has both oxygen ion (oxide ion) conductivity and electron conductivity,namely mixed conductivity. The intermediate layer 3 that has theseproperties is suitable for application to the electrochemical element E.

Electrolyte Layer

As shown in FIG. 1, the electrolyte layer 4 is formed as a thin layeron/over the intermediate layer 3 so as to cover the electrode layer 2and the intermediate layer 3. The electrolyte layer 4 can also be formedas a thin film having a thickness of 10 μm or less. Specifically, asshown in FIG. 1, the electrolyte layer 4 is provided on/over both theintermediate layer 3 and the metal substrate 1 (spanning theintermediate layer 3 and the metal substrate 1). Configuring theelectrolyte layer 4 in this manner and joining the electrolyte layer 4to the metal substrate 1 make it possible to allow the electrochemicalelement to have excellent toughness as a whole.

Also, as shown in FIG. 1, the electrolyte layer 4 is provided in aregion that is larger than the region provided with the through holes 1a, on/over the front surface of the metal substrate 1. That is, thethrough holes 1 a are formed inside the region of the metal substrate 1in which the electrolyte layer 4 is formed.

The leakage of gas from the electrode layer 2 and the intermediate layer3 can be suppressed in the vicinity of the electrolyte layer 4. Adescription of this will be given. When the electrochemical element E isused as a constituent element of a SOFC, gas is supplied from the backside of the metal substrate 1 through the through holes 1 a to theelectrode layer 2 during the operation of the SOFC. In a region wherethe electrolyte layer 4 is in contact with the metal substrate 1,leakage of gas can be suppressed without providing another componentsuch as a gasket. It should be noted that although the entire vicinityof the electrode layer 2 is covered with the electrolyte layer 4 in thisembodiment, a configuration in which the electrolyte layer 4 is providedon/over the electrode layer 2 and the intermediate layer 3 and a gasketor the like is provided in its vicinity may also be adopted.

YSZ (yttria-stabilized zirconia), SSZ (scandium-stabilized zirconia),GDC (gadolinium-doped ceria), YDC (yttrium-doped ceria), SDC(samarium-doped ceria), LSGM (strontium- and magnesium-doped lanthanumgallate), or the like can be used as the material for forming theelectrolyte layer 4. In particular, zirconia-based ceramics arefavorably used. Using zirconia-based ceramics for the electrolyte layer4 makes it possible to increase the operation temperature of the SOFC inwhich the electrochemical element E is used compared with the case whereceria-based ceramics are used. For example, when the electrochemicalelement E is used in the SOFC, by adopting a system configuration inwhich a material such as YSZ that can exhibit high electrolyteperformance even in a high temperature range of approximately 650° C. orhigher is used as the material for forming the electrolyte layer 4, ahydrocarbon-based raw fuel material such as city gas or LPG is used asthe raw fuel for the system, and the raw fuel material is reformed intoanode gas of the SOFC through steam reforming or the like, it is thuspossible to construct a high-efficiency SOFC system in which heatgenerated in a cell stack of the SOFC is used to reform raw fuel gas.

It is preferable to form the electrolyte layer 4 using low-temperatureheating (not performing heating treatment in a high temperature range ofhigher than 1100° C., but rather performing a wet process using heatingtreatment in a low temperature range, for example), a spray coatingtechnique (a technique such as a thermal spraying technique, an aerosoldeposition technique, an aerosol gas deposition technique, a powder jetdeposition technique, a particle jet deposition technique, or a coldspraying technique), a PVD technique (e.g., a sputtering technique or apulse laser deposition technique), a CVD technique, or the like. Due tothese film formation processes that can be used in a low temperaturerange, an electrolyte layer 4 that is dense and has high gas-tightnessand gas barrier properties is obtained without using heating in a hightemperature range of higher than 1100° C., for example. Therefore, it ispossible to prevent damage to the metal substrate 1, suppress elementinterdiffusion between the metal substrate 1 and the electrode layer 2,and realize an electrochemical element E that has excellent performanceand durability. In particular, using low-temperature heating, a spraycoating technique, or the like makes it possible to realize a low-costelement and is thus preferable. Furthermore, using a spray coatingtechnique makes it easy to obtain, in a low temperature range, anelectrolyte layer that is dense and has high gas-tightness and gasbarrier properties, and is thus more preferable.

The electrolyte layer 4 is given a dense configuration in order to blockgas leakage of anode gas and cathode gas and exhibit high ionconductivity. The electrolyte layer 4 preferably has a denseness of 90%or more, more preferably 95% or more, and even more preferably 98% ormore. When the electrolyte layer 4 is formed as a uniform layer, thedenseness is preferably 95% or more, and more preferably 98% or more.When the electrolyte layer 4 has a multilayer configuration, at least aportion thereof preferably includes a layer (dense electrolyte layer)having a denseness of 98% or more, and more preferably a layer (denseelectrolyte layer) having a denseness of 99% or more. The reason forthis is that an electrolyte layer that is dense and has highgas-tightness and gas barrier properties can be easily formed due tosuch a dense electrolyte layer being included as a portion of theelectrolyte layer even when the electrolyte layer has a multilayerconfiguration.

Reaction Preventing Layer

The reaction preventing layer 5 can be formed as a thin layer on/overthe electrolyte layer 4. When it is formed as a thin layer, thethickness can be set to approximately 1 μm to 100 μm, preferablyapproximately 2 μm to 50 μm, and more preferably approximately 4 μm to25 μm, for example. This thickness makes it possible to ensuresufficient performance while also achieving cost reduction by reducingthe used amount of expensive reaction preventing layer material. Thematerial for forming the reaction preventing layer 5 need only becapable of preventing reactions between the component of the electrolytelayer 4 and the component of the counter electrode layer 6. For example,a ceria-based material or the like is used. Introducing the reactionpreventing layer 5 between the electrolyte layer 4 and the counterelectrode layer 6 effectively suppresses reactions between the materialconstituting the counter electrode layer 6 and the material constitutingthe electrolyte layer 4 and makes it possible to improve long-termstability in the performance of the electrochemical element E. Formingthe reaction preventing layer 5 using, as appropriate, a method throughwhich the reaction preventing layer 5 can be formed at a treatmenttemperature of 1100° C. or lower makes it possible to suppress damage tothe metal substrate 1, suppress element interdiffusion between the metalsubstrate 1 and the electrode layer 2, and realize an electrochemicalelement E that has excellent performance and durability, and is thuspreferable. For example, the reaction preventing layer 5 can be formedusing, as appropriate, low-temperature heating (not performing heatingtreatment in a high temperature range of higher than 1100° C., butrather performing a wet process using heating treatment in a lowtemperature range, for example), a spray coating technique (a techniquesuch as a thermal spraying technique, an aerosol deposition technique,an aerosol gas deposition technique, a powder jet deposition technique,a particle jet deposition technique, or a cold spraying technique), aPVD technique (e.g., a sputtering technique or a pulse laser depositiontechnique), a CVD technique, or the like. In particular, usinglow-temperature heating, a spray coating technique, or the like makes itpossible to realize a low-cost element and is thus preferable.Furthermore, using low-temperature heating makes it possible tofacilitate handling of raw materials and is thus more preferable.

Counter Electrode Layer

The counter electrode layer 6 can be formed as a thin layer on/over theelectrolyte layer 4 or the reaction preventing layer 5. When it isformed as a thin layer, the thickness can be set to approximately 1 μmto 100 μm, and preferably approximately 5 μm to 50 μm, for example. Thisthickness makes it possible to ensure sufficient electrode performancewhile also achieving cost reduction by reducing the used amount ofexpensive counter electrode layer material. A complex oxide such as LSCFor LSM, or a ceria-based oxide, or a mixture thereof can be used as thematerial for forming the counter electrode layer 6, for example. Inparticular, it is preferable that the counter electrode layer 6 includesa perovskite oxide containing two or more elements selected from thegroup consisting of La, Sr, Sm, Mn, Co, and Fe. The counter electrodelayer 6 constituted by the above-mentioned material functions as acathode.

It should be noted that forming the counter electrode layer 6 using, asappropriate, a method through which the counter electrode layer 6 can beformed at a treatment temperature of 1100° C. or lower makes it possibleto suppress damage to the metal substrate 1, suppress elementinterdiffusion between the metal substrate 1 and the electrode layer 2,and realize an electrochemical element E that has excellent performanceand durability, and is thus preferable. For example, the counterelectrode layer 6 can be formed using, as appropriate, low-temperatureheating (not performing heating treatment in a high temperature range ofhigher than 1100° C., but rather performing a wet process using heatingtreatment in a low temperature range, for example), a spray coatingtechnique (a technique such as a thermal spraying technique, an aerosoldeposition technique, an aerosol gas deposition technique, a powder jetdeposition technique, a particle jet deposition technique, or a coldspraying technique), a PVD technique (e.g., a sputtering technique or apulse laser deposition technique), a CVD technique, or the like. Inparticular, using low-temperature heating, a spray coating technique, orthe like makes it possible to realize a low-cost element and is thuspreferable. Furthermore, using low-temperature heating makes it possibleto facilitate handling of raw materials and is thus more preferable.

Solid Oxide Fuel Cell

The electrochemical element E configured as described above can be usedas a power generating cell for a solid oxide fuel cell. For example,fuel gas containing hydrogen is supplied from the back surface of themetal substrate 1 through the through holes 1 a to the electrode layer2, air is supplied to the counter electrode layer 6 serving as a counterelectrode of the electrode layer 2, and the operation is performed at atemperature of 600° C. or higher and 850° C. or lower, for example.Accordingly, the oxygen O₂ included in air reacts with electrons e⁻ inthe counter electrode layer 6, thus producing oxygen ions O²⁻. Theoxygen ions O²⁻ move through the electrolyte layer 4 to the electrodelayer 2. In the electrode layer 2, the hydrogen H₂ included in thesupplied fuel gas reacts with the oxygen ions O²⁻, thus producing waterH₂O and electrons e⁻. With these reactions, electromotive force isgenerated between the electrode layer 2 and the counter electrode layer6. In this case, the electrode layer 2 functions as a fuel electrode(anode) of the SOFC, and the counter electrode layer 6 functions as anair electrode (cathode).

Manufacturing Method for Electrochemical Element

Next, a manufacturing method for the electrochemical element E accordingto this embodiment will be described.

Electrode Layer Forming Step

In an electrode layer forming step, the electrode layer 2 is formed as athin film in a region that is broader than the region provided with thethrough holes 1 a, on/over the front surface of the metal substrate 1.The through holes of the metal substrate 1 can be provided through laserprocessing or the like. As described above, the electrode layer 2 can beformed using low-temperature heating (a wet process using heatingtreatment in a low temperature range of 1100° C. or lower), a spraycoating technique (a technique such as a thermal spraying technique, anaerosol deposition technique, an aerosol gas deposition technique, apowder jet deposition technique, a particle jet deposition technique, ora cold spraying technique), a PVD technique (e.g., a sputteringtechnique or a pulse laser deposition technique), a CVD technique, orthe like. Regardless of which technique is used, it is desirable toperform the technique at a temperature of 1100° C. or lower in order tosuppress deterioration of the metal substrate 1.

The following is an example of the case where low-temperature heating isperformed as the electrode layer forming step. First, a material pasteis produced by mixing powder of the material for forming the electrodelayer 2 and a solvent (dispersion medium), and is applied to the frontsurface of the metal substrate 1. Then, the electrode layer 2 isobtained through compression shape forming (electrode layer smoothingstep) and heating at a temperature of 1100° C. or lower (electrode layerheating step). Examples of compression shape forming of the electrodelayer 2 include CIP (Cold Isostatic Pressing) shape forming, rollpressing shape forming, and RIP (Rubber Isostatic Pressing) shapeforming. It is favorable to perform heating of the electrode layer 2 ata temperature of 800° C. or higher and 1100° C. or lower. The order inwhich the electrode layer smoothing step and the electrode layer heatingstep are performed can be changed.

It should be noted that, when an electrochemical element including anintermediate layer is formed, the electrode layer smoothing step and theelectrode layer heating step may be omitted, and an intermediate layersmoothing step and an intermediate layer heating step, which will bedescribed later, may include the electrode layer smoothing step and theelectrode layer heating step.

It should be noted that lapping shape forming, leveling treatment,surface cutting treatment, surface polishing treatment, or the like canalso be performed as the electrode layer smoothing step.

Diffusion Suppressing Layer Forming Step

The metal oxide thin layer 1 b (diffusion suppressing layer (thinlayer)) is formed on/over the surface of the metal substrate 1 duringthe heating step in the above-described electrode layer forming step. Itshould be noted that it is preferable that the above-mentioned heatingstep includes a heating step in which the heating atmosphere satisfiesthe atmospheric condition that the oxygen partial pressure is lowbecause a high-quality metal oxide thin layer 1 b (diffusion suppressinglayer) that has a high element interdiffusion suppressing effect and hasa low resistance value is formed. In a case where a coating method thatdoes not include heating is performed as the electrode layer formingstep, for example, a separate diffusion suppressing layer forming stepmay also be included. For example, in the separate diffusion suppressinglayer forming step, the metal oxide thin layer 1 b (diffusionsuppressing layer (thin layer)) is formed by coating the metal substrate1 with Co and then performing oxidation treatment. Alternatively, forexample, in the separate diffusion suppressing layer forming step, themetal oxide thin layer 1 b (diffusion suppressing layer (thin layer)) isformed by coating the interposing layer formed on/over the metalsubstrate 1 with Co and then performing oxidation treatment.

In any case, it is desirable to perform these steps at a temperature of1100° C. or lower such that damage to the metal substrate 1 can besuppressed. The metal oxide thin layer 1 b (diffusion suppressing layer)may be formed on/over the surface of the metal substrate 1 during theheating step in an intermediate layer forming step, which will bedescribed later.

Intermediate Layer Forming Step

In an intermediate layer forming step, the intermediate layer 3 isformed as a thin layer on/over the electrode layer 2 so as to cover theelectrode layer 2. As described above, the intermediate layer 3 can beformed using low-temperature heating (a wet process using heatingtreatment in a low temperature range of 1100° C. or lower), a spraycoating technique (a technique such as a thermal spraying technique, anaerosol deposition technique, an aerosol gas deposition technique, apowder jet deposition technique, a particle jet deposition technique, ora cold spraying technique), a PVD technique (e.g., a sputteringtechnique or a pulse laser deposition technique), a CVD technique, orthe like. Regardless of which technique is used, it is desirable toperform the technique at a temperature of 1100° C. or lower in order tosuppress deterioration of the metal substrate 1.

The following is an example of the case where low-temperature heating isperformed as the intermediate layer forming step. First, a materialpaste is produced by mixing powder of the material for forming theintermediate layer 3 and a solvent (dispersion medium), and is appliedto the front surface of the metal substrate 1. Then, the intermediatelayer 3 is obtained through compression shape forming (intermediatelayer smoothing step) and heating at a temperature of 1100° C. or lower(intermediate layer heating step). Examples of rolling of theintermediate layer 3 include CIP (Cold Isostatic Pressing) shapeforming, roll pressing shape forming, and RIP (Rubber IsostaticPressing) shape forming. It is favorable to perform heating of theintermediate layer at a temperature of 800° C. or higher and 1100° C. orlower. The reason for this is that this temperature makes it possible toform an intermediate layer 3 that has high strength while suppressingdamage to and deterioration of the metal substrate 1. It is morepreferable to perform heating of the intermediate layer 3 at atemperature of 1050° C. or lower, and more preferably 1000° C. or lower.The reason for this is that the lower the heating temperature of theintermediate layer 3 is, the more likely it is to further suppressdamage to and deterioration of the metal substrate 1 when forming theelectrochemical element E. The order in which the intermediate layersmoothing step and the intermediate layer heating step are performed canbe changed.

It should be noted that lapping shape forming, leveling treatment,surface cutting treatment, surface polishing treatment, or the like canalso be performed as the intermediate layer smoothing step.

Electrolyte Layer Forming Step

In an electrolyte layer forming step, the electrolyte layer 4 is formedas a thin layer on/over the intermediate layer 3 so as to cover theelectrode layer 2 and the intermediate layer 3. The electrolyte layer 4may also be formed as a thin film having a thickness of 10 μm or less.As described above, the electrolyte layer 4 can be formed usinglow-temperature heating (a wet process using heating treatment in a lowtemperature range of 1100° C. or lower), a spray coating technique (atechnique such as a thermal spraying technique, an aerosol depositiontechnique, an aerosol gas deposition technique, a powder jet depositiontechnique, a particle jet deposition technique, or a cold sprayingtechnique), a PVD technique (e.g., a sputtering technique or a pulselaser deposition technique), a CVD technique, or the like. Regardless ofwhich technique is used, it is desirable to perform the technique at atemperature of 1100° C. or lower in order to suppress deterioration ofthe metal substrate 1.

It is desirable to perform a spray coating technique as the electrolytelayer forming step in order to form a high-quality electrolyte layer 4that is dense and has high gas-tightness and gas barrier properties in atemperature range of 1100° C. or lower. In this case, the material forforming the electrolyte layer 4 is sprayed onto the intermediate layer 3on/over the metal substrate 1, and the electrolyte layer 4 is thusformed.

Reaction Preventing Layer Forming Step

In a reaction preventing layer forming step, the reaction preventinglayer 5 is formed as a thin layer on/over the electrolyte layer 4. Asdescribed above, the reaction preventing layer 5 can be formed usinglow-temperature heating, a spray coating technique (a technique such asa thermal spraying technique, an aerosol deposition technique, anaerosol gas deposition technique, a powder jet deposition technique, aparticle jet deposition technique, or a cold spraying technique), a PVDtechnique (e.g., a sputtering technique or a pulse laser depositiontechnique), a CVD technique, or the like. Regardless of which techniqueis used, it is desirable to perform the technique at a temperature of1100° C. or lower in order to suppress deterioration of the metalsubstrate 1. It should be noted that leveling treatment, surface cuttingtreatment, or surface polishing treatment may be performed after theformation of the reaction preventing layer 5, or pressing processing maybe performed after wet formation and before heating in order to flattenthe upper surface of the reaction preventing layer 5.

Counter Electrode Layer Forming Step

In a counter electrode layer forming step, the counter electrode layer 6is formed as a thin layer on/over the reaction preventing layer 5. Asdescribed above, the counter electrode layer 6 can be formed usinglow-temperature heating, a spray coating technique (a technique such asa thermal spraying technique, an aerosol deposition technique, anaerosol gas deposition technique, a powder jet deposition technique, aparticle jet deposition technique, or a cold spraying technique), a PVDtechnique (e.g., a sputtering technique or a pulse laser depositiontechnique), a CVD technique, or the like. Regardless of which techniqueis used, it is desirable to perform the technique at a temperature of1100° C. or lower in order to suppress deterioration of the metalsubstrate 1.

In this manner, the electrochemical element E can be manufactured. Itshould be noted that the substrate with an electrode layer B for ametal-supported electrochemical element can be manufactured byperforming the above-described electrode layer forming step andintermediate layer forming step. That is, the manufacturing methodaccording to this embodiment is a method for manufacturing a substratewith an electrode layer B for a metal-supported electrochemical element,the substrate including a metal substrate 1 (metal support), anelectrode layer 2 formed on/over the metal substrate 1, and anintermediate layer 3 formed on/over the electrode layer 2, and themethod includes an intermediate layer smoothing step of smoothing thesurface of the intermediate layer 3 and an intermediate layer heatingstep of performing heating of the intermediate layer 3 at a temperatureof 1100° C. or lower.

It should be noted that a configuration in which the electrochemicalelement E does not include both or either of the intermediate layer 3and the reaction preventing layer 5 is also possible. That is, aconfiguration in which the electrode layer 2 and the electrolyte layer 4are in contact with each other, or a configuration in which theelectrolyte layer 4 and the counter electrode layer 6 are in contactwith each other is also possible. In this case, in the above-describedmanufacturing method, the intermediate layer forming step and thereaction preventing layer forming step are omitted. It should be notedthat it is also possible to add a step of forming another layer or toform a plurality of layers of the same type one on/over top of another,but in any case, it is desirable to perform these steps at a temperatureof 1100° C. or lower.

Third Embodiment

An electrochemical element E, an electrochemical module M, anelectrochemical device Y, and an energy system Z according to thisembodiment will be described with reference to FIGS. 2 and 3.

As shown in FIG. 2, in the electrochemical element E according to thisembodiment, a U-shaped component 7 is attached to the back surface ofthe metal substrate 1, and the metal substrate 1 and the U-shapedcomponent 7 form a tubular support. The above-described alloy materialis used for the U-shaped component 7 (separator).

The electrochemical module M is configured by stacking a plurality ofelectrochemical elements E with current collectors 26 being sandwichedtherebetween. Each of the current collector 26 is joined to the counterelectrode layer 6 of the electrochemical element E and the U-shapedcomponent 7, and electrically connects them. The above-described alloymaterial is used for the current collector 26.

The electrochemical module M includes a gas manifold 17, the currentcollectors 26, a terminal component, and a current extracting unit. Oneopen end of each tubular support in the stack of the plurality ofelectrochemical elements E is connected to the gas manifold 17, and gasis supplied from the gas manifold 17 to the electrochemical elements E.The supplied gas flows inside the tubular supports, and is supplied tothe electrode layers 2 through the through holes 1 a of the metalsubstrates 1. The above-described alloy material is used for the gasmanifold 17 (manifold).

It should be noted that the above-described alloy material may be usedfor at least one of the separator (U-shaped component 7), the manifold(gas manifold 17), and the current collector 26.

FIG. 3 shows an overview of the energy system Z and the electrochemicaldevice Y.

The energy system Z includes the electrochemical device Y, and a heatexchanger 53 serving as a waste heat management unit that reuses heatdischarged from the electrochemical device Y.

The electrochemical device Y includes the electrochemical module M, anda fuel supply unit that includes a desulfurizer 31, and a reformer 34and supplies fuel gas containing a reducible component to theelectrochemical module M, and the electrochemical device Y includes aninverter 38 that extracts electrical power from the electrochemicalmodule M.

Specifically, the electrochemical device Y includes the desulfurizer 31,a reformed water tank (water tank for reforming process) 32, a vaporizer33, the reformer 34, a blower 35, a combustion unit 36, the inverter 38,a control unit 39, a storage container 40, and the electrochemicalmodule M.

The desulfurizer 31 removes sulfur compound components contained in ahydrocarbon-based raw fuel such as city gas (i.e., performsdesulfurization). When a sulfur compound is contained in the raw fuel,the inclusion of the desulfurizer 31 makes it possible to suppress theinfluence that the sulfur compound has on the reformer 34 or theelectrochemical elements E. The vaporizer 33 produces water vapor fromreformed water supplied from the reformed water tank 32. The reformer 34uses the water vapor produced by the vaporizer 33 to perform steamreforming of the raw fuel desulfurized by the desulfurizer 31, thusproducing reformed gas containing hydrogen.

The electrochemical module M generates electricity by causing anelectrochemical reaction to occur with use of the reformed gas suppliedfrom the reformer 34 and air supplied from the blower 35. The combustionunit 36 mixes the reaction exhaust gas discharged from theelectrochemical module M with air, and burns combustible components inthe reaction exhaust gas.

The electrochemical module M includes a plurality of electrochemicalelements E and the gas manifold 17. The electrochemical elements E arearranged side-by-side and electrically connected to each other, and oneend portion (lower end portion) of each of the electrochemical elementsE is fixed to the gas manifold 17. The electrochemical elements Egenerate electricity by causing an electrochemical reaction to occurbetween the reformed gas supplied via the gas manifold 17 and airsupplied from the blower 35.

The inverter 38 adjusts the electrical power output from theelectrochemical module M to obtain the same voltage and frequency aselectrical power received from a commercial system (not shown). Thecontrol unit 39 controls the operation of the electrochemical device Yand the energy system Z.

The vaporizer 33, the reformer 34, the electrochemical module M, and thecombustion unit 36 are stored in the storage container 40. The reformer34 performs reformation processing on the raw fuel with use ofcombustion heat produced by the combustion of reaction exhaust gas inthe combustion unit 36.

The raw fuel is supplied to the desulfurizer 31 via a raw fuel supplypassage 42, due to operation of a booster pump 41. The reformed water inthe reformed water tank 32 is supplied to the vaporizer 33 via areformed water supply passage 44, due to operation of a reformed waterpump 43. The raw fuel supply passage 42 merges with the reformed watersupply passage 44 at a location on the downstream side of thedesulfurizer 31, and the reformed water and the raw fuel, which havebeen merged outside of the storage container 40, are supplied to thevaporizer 33 provided in the storage container 40.

The reformed water is vaporized by the vaporizer 33 to produce watervapor. The raw fuel, which contains the water vapor produced by thevaporizer 33, is supplied to the reformer 34 via a vapor-containing rawfuel supply passage 45. In the reformer 34, the raw fuel is subjected tosteam reforming, thus producing reformed gas that includes hydrogen gasas a main component (first gas including a reducible component). Thereformed gas produced in the reformer 34 is supplied to the gas manifold17 of the electrochemical module M via a reformed gas supply passage 46.

The reformed gas supplied to the gas manifold 17 is distributed amongthe electrochemical elements E, and is supplied to the electrochemicalelements E from the lower ends, which are the connection portions wherethe electrochemical elements E and the gas manifold 17 are connected toeach other. Mainly the hydrogen (reducible component) in the reformedgas is used in the electrochemical reaction in the electrochemicalelements E. The reaction exhaust gas, which contains remaining hydrogengas not used in the reaction, is discharged from the upper ends of theelectrochemical elements E to the combustion unit 36.

The reaction exhaust gas is burned in the combustion unit 36, andcombustion exhaust gas is discharged from a combustion exhaust gasoutlet 50 to the outside of the storage container 40. A combustioncatalyst unit 51 (e.g., a platinum-based catalyst) is provided in thecombustion exhaust gas outlet 50, and reducible components such ascarbon monoxide and hydrogen contained in the combustion exhaust gas areremoved by combustion. The combustion exhaust gas discharged from thecombustion exhaust gas outlet 50 is sent to the heat exchanger 53 via acombustion exhaust gas discharge passage 52.

The heat exchanger 53 uses supplied cool water to perform heat exchangeon the combustion exhaust gas produced by combustion in the combustionunit 36, thus producing warm water. In other words, the heat exchanger53 operates as a waste heat management unit that reuses heat dischargedfrom the electrochemical device Y.

It should be noted that instead of the waste heat management unit, it ispossible to provide a reaction exhaust gas using unit that uses thereaction exhaust gas that is discharged from (not burned in) theelectrochemical module M. The reaction exhaust gas contains remaininghydrogen gas that was not used in the reaction in the electrochemicalelements E. In the reaction exhaust gas using unit, the remaininghydrogen gas is used to achieve effective energy utilization by heatutilization through combustion, power generation in a fuel cell, or thelike.

Fourth Embodiment

FIG. 4 shows another embodiment of the electrochemical module M. Theelectrochemical module M according to this embodiment is configured bystacking the above-described electrochemical elements E with cellconnecting components 71 being sandwiched therebetween.

The cell connecting components 71 are each a plate-shaped component thathas electron conductivity and does not have gas permeability, and theupper surface and the lower surface are respectively provided withgrooves 72 that are orthogonal to each other. The cell connectingcomponents 71 can be formed using a metal such as stainless steel or ametal oxide. The above-mentioned alloy material is used for the cellconnecting components 71 (interconnectors).

As shown in FIG. 4, when the electrochemical elements E are stacked withthe cell connecting components 71 being sandwiched therebetween, a gascan be supplied to the electrochemical elements E through the grooves72. Specifically, the grooves 72 on one side are first gas passages 72 aand supply gas to the front side of one electrochemical element E, thatis to say the counter electrode layer 6. The grooves 72 on the otherside are second gas passages 72 b and supply gas from the back side ofone electrochemical element E, that is, the back side of the metalsubstrate 1, through the through holes 1 a to the electrode layers 2.

In the case of operating this electrochemical module M as a fuel cell,oxygen is supplied to the first gas passages 72 a, and hydrogen issupplied to the second gas passages 72 b. Accordingly, a fuel cellreaction progresses in the electrochemical elements E, and electromotiveforce and electrical current are generated. The generated electricalpower is extracted to the outside of the electrochemical module M fromthe cell connecting components 71 at the two ends of the stack ofelectrochemical elements E.

It should be noted that although the grooves 72 that are orthogonal toeach other are respectively formed on the front surface and the backsurface of each of the cell connecting components 71 in this embodiment,grooves 72 that are parallel to each other can be respectively formed onthe front surface and the back surface of each of the cell connectingcomponents 71.

OTHER EMBODIMENTS

(1) Although the electrochemical elements E are used in a solid oxidefuel cell in the above-described embodiments, the electrochemicalelements E can also be used in a solid oxide electrolytic cell, anoxygen sensor using a solid oxide, and the like. Moreover, the alloymaterial of the present invention can also be used in various devices inwhich volatilization of Cr from components needs to be suppressed,particularly various devices that are operated in a high-temperaturerange, other than the electrochemical element.

(2) Although the present application is applied to a metal-supportedsolid oxide fuel cell in which the metal substrate 1 serves as a supportin the above-described embodiments, the present application can also beapplied to an electrode-supported solid oxide fuel cell in which theelectrode layer 2 or counter electrode layer 6 serves as a support, oran electrolyte-supported solid oxide fuel cell in which the electrolytelayer 4 serves as a support. In such cases, the functions of a supportcan be obtained by forming the electrode layer 2, counter electrodelayer 6, or electrolyte layer 4 to have a required thickness.

(3) In the above-described embodiments, a composite material such asNiO-GDC, Ni-GDC, NiO-YSZ, Ni-YSZ, CuO—CeO₂, or Cu—CeO₂ is used as thematerial for forming the electrode layer 2, and a complex oxide such asLSCF or LSM is used as the material for forming the counter electrodelayer 6. With this configuration, the electrode layer 2 serves as a fuelelectrode (anode) when hydrogen gas is supplied thereto, and the counterelectrode layer 6 serves as an air electrode (cathode) when air issupplied thereto, thus making it possible to use the electrochemicalelement E as a cell for a solid oxide fuel cell. It is also possible tochange this configuration and thus configure an electrochemical elementE such that the electrode layer 2 can be used as an air electrode andthe counter electrode layer 6 can be used as a fuel electrode. That is,a complex oxide such as LSCF or LSM is used as the material for formingthe electrode layer 2, and a composite material such as NiO-GDC, Ni-GDC,NiO-YSZ, Ni-YSZ, CuO—CeO₂, or Cu—CeO₂ is used as the material forforming the counter electrode layer 6. With this configuration, theelectrode layer 2 serves as an air electrode when air is suppliedthereto, and the counter electrode layer 6 serves as a fuel electrodewhen hydrogen gas is supplied thereto, thus making it possible to usethe electrochemical element E as a cell for a solid oxide fuel cell.

It should be noted that the configurations disclosed in theabove-described embodiments can be used in combination withconfigurations disclosed in other embodiments as long as they arecompatible with each other. The embodiments disclosed in thisspecification are illustrative, and embodiments of the present inventionare not limited thereto and can be modified as appropriate withoutdeparting from the object of the present invention.

INDUSTRIAL APPLICABILITY

The present invention can be applied to an electrochemical element and acell for a solid oxide fuel cell.

LIST OF REFERENCE NUMERALS

-   -   1: Metal substrate (metal support, alloy material)    -   1 a: Through hole    -   2: Electrode layer    -   3: Intermediate layer    -   4: Electrolyte layer    -   5: Reaction preventing layer    -   6: Counter electrode layer    -   7: U-shaped component (separator, alloy material)    -   17: Gas manifold (manifold, alloy material)    -   26: Current collector (alloy material)    -   31: Desulfurizer    -   32: Reformed water tank    -   33: Vaporizer    -   34: Reformer    -   35: Blower    -   36: Combustion unit    -   38: Inverter    -   39: Control unit    -   40: Storage container    -   41: Booster pump    -   42: Raw fuel supply passage    -   43: Reformed water pump    -   44: Reformed water supply passage    -   45: Vapor-containing raw fuel supply passage    -   46: Reformed gas supply passage    -   50: Combustion exhaust gas outlet    -   51: Combustion catalyst unit    -   52: Combustion exhaust gas discharge passage    -   53: Heat exchanger    -   71: Cell connecting component (interconnector, alloy material)    -   72: Groove    -   72 a: First gas passage    -   72 b: Second gas passage    -   E: Electrochemical element    -   M: Electrochemical module    -   y: Electrochemical device    -   Z: Energy system

1. A manufacturing method for an alloy material comprising: a coatingtreatment step for coating a substrate made of a Fe—Cr based alloy withCo; and an oxidation treatment step for performing oxidation treatmenton the substrate in a moisture-containing atmosphere after the coatingtreatment step.
 2. The manufacturing method for an alloy materialaccording to claim 1, wherein coating with Co is performed throughplating treatment in the coating treatment step.
 3. The manufacturingmethod for an alloy material according to claim 1, wherein the oxidationtreatment step is performed in an atmosphere having a dew point of 25°C. or higher.
 4. An alloy material comprising: a substrate made of aFe—Cr based alloy; and a thin layer formed on/over the substrate,wherein the thin layer contains Co, and a Co-containing region is formedin the vicinity of a surface inside the substrate.
 5. An alloy materialcomprising: a substrate made of a Fe—Cr based alloy; and a thin layerformed on/over the substrate, wherein the thin layer includes a firstlayer and a second layer, the first layer is formed on/over thesubstrate and is made of a metal oxide that contains Cr, and the secondlayer is formed on/over the first layer as a metal oxide thin layer thatcontains Co.
 6. The alloy material according to claim 5, wherein aCo-containing region is formed in the vicinity of a surface inside thesubstrate.
 7. The alloy material according to claim 5, wherein thesecond layer contains Mn.
 8. The alloy material according to claim 4,wherein the Fe—Cr based alloy of the substrate contains Mn in an amountof 0.05 mass % or more.
 9. The alloy material according to claim 4,wherein the Fe—Cr based alloy of the substrate is any one of a Fe—Crbased alloy that contains Ti in an amount of 0.15 mass % or more and 1.0mass % or less, a Fe—Cr based alloy that contains Zr in an amount of0.15 mass % or more and 1.0 mass % or less, and a Fe—Cr based alloy thatcontains Ti and Zr, the total content of Ti and Zr being 0.15 mass % ormore and 1.0 mass % or less.
 10. The alloy material according to claim4, wherein the Fe—Cr based alloy of the substrate contains Cu in anamount of 0.10 mass % or more and 1.0 mass % or less.
 11. The alloymaterial according to claim 4, wherein the Fe—Cr based alloy of thesubstrate contains Cr in an amount of 18 mass % or more and 25 mass % orless.
 12. An electrochemical element in which at least an electrodelayer, an electrolyte layer, and a counter electrode layer are providedon/over the alloy material according to claim
 4. 13. An electrochemicalmodule in which a plurality of the electrochemical elements according toclaim 12 are arranged in an assembled state.
 14. An electrochemicaldevice comprising at least the electrochemical module according to claim13 and a reformer and comprising a fuel supply unit which supplies fuelgas containing a reducible component to the electrochemical module. 15.An electrochemical device comprising at least the electrochemical moduleaccording to claim 13 and an inverter that extracts electrical powerfrom the electrochemical module.
 16. An electrochemical devicecomprising at least one of a separator, a manifold, an interconnector,and a current collector, wherein at least one of the separator, themanifold, the interconnector, and the current collector is formed of thealloy material according to claim
 4. 17. An energy system comprising:the electrochemical device according to claim 14; and a waste heatmanagement unit that reuses heat discharged from the electrochemicaldevice.
 18. A solid oxide fuel cell comprising the electrochemicalelement according to claim 12, wherein a power generation reaction iscaused in the electrochemical element.